JPS5920015A - Controller for temperature of heating furnace - Google Patents

Abstract

PURPOSE:To allow the temperature to fall to a temperature for keeping warm in a short time, by outputting the operation output value from an independently provided manipulated variable setter when the deviation from a temperature measured value is larger than a prescribed value and switching the output to the output from a PID operator when this deviation is smaller than the prescribed value. CONSTITUTION:An intra-furnace temperature set value 10 is set to the temperature for keeping warm and is detected by a lower limit alarm device 13. The output of a deviation operator 12 is detected by an upper limit alarm device 14. AND between a switch signal of an interlock 15, which determines whether minimum flow setting is performed or not through the logic operation, and output signals of alarm devices 13 and 14 is operated in an AND gate 16, and a switch 18 is switched to the side of a terminal (a) to the side of a terminal (b) by this gate output. Thus, the signal to an output processing part 19 is switched to the signal obtained by allowing a signal from a preliminarily set minimum setter 20 to pass through the side of the terminal (b) of a switch 23. The minimum set value of the setter 20 is set to a minimum set value where combustion in the furnace is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a heating furnace, particularly when the heating furnace is used as a patch-type heating furnace in which the insert to be heat-treated in the furnace is temporarily interrupted. The present invention relates to a temperature control device suitable for use when

Conventionally, in this type of batch-type heating furnace, when there are no more inserts in the furnace, leaving P to continue burning would result in a loss of fuel, so the temperature of the furnace was lowered using refractory bricks or other materials. Due to the characteristics of the furnace, it is required to temporarily lower the temperature to a level at which it must be kept warm. In this case, conventionally, the purpose was achieved by setting the first shift of the PID calculator of the temperature controller that normally controls the temperature to the temperature that should be lowered. Since the PID control circuit operates until the internal temperature drops to the target temperature, the operating output will be hunting, and it will take a long time to drop to the target temperature, resulting in high fuel consumption and overcooling. There is.

This was developed in consideration of the above, and its purpose is to reduce the temperature inside the heating furnace in a short period of time to the temperature at which it is kept warm during normal operation, thereby significantly reducing wasteful consumption of fuel. An object of the present invention is to provide a heating furnace temperature control device that can reduce the temperature of a heating furnace.

A feature of the present invention is that when the temperature in the furnace temperature setting for one shift is less than or equal to the predetermined lower limit of one shift and the deviation from the temperature measurement for one shift is greater than or equal to a predetermined value, P I I) Set the arithmetic unit in an integral-separation state and output one operation completion signal from the separately provided manipulated variable setter from the temperature controller, during which time the manipulated output value is input to the P I I) operator. The above deviation is the above specified (if it is under direct sales, the above P I ]) solves the integral separation of the arithmetic unit,
The above operation output value that had been output until then is converted to the above P I
The point is that a means is provided for converting the output from the D calculator into ψ.

Hereinafter, the present invention will be explained by the embodiments shown in FIGS.
This will be explained in detail using figures.

FIG. 1 is a system configuration diagram showing an embodiment of the temperature control device of the present invention. In FIG. 1, 1 is a heating furnace, and 2 is a temperature detection terminal provided in the heating furnace 1. The temperature controller 4 compares it with the set point, and the output after J]ID calculation is given by the function i1*Jf unit 5.
and is output to the fuel control valve 6. The function calculator 5 calculates the amount of combustion air commensurate with the fuel, and outputs the output to the combustion air control valve 7. The fuel 8 that has passed through the combustion control valve 6 and the combustion air 9 that has passed through the combustion air control valve 7 are mixed and burned in a burner.

FIG. 2 is a block diagram showing an embodiment of the temperature controller 4 shown in FIG. 1. Furnace temperature setting 1l NIO and furnace temperature measurement l
lI! (Output of temperature converter 3) 11 means deviation calculator 1
2, SV (warm face setting 1li) P■ (temperature measurement box) is calculated, and the effect is P I 1) Calculator 1
7. The output of the PiD calculator 17 normally passes through the terminal side of the switch 18 and reaches the output processing section 19.
The output processing section 19 outputs the signal as a valve operation signal.

Here, when transitioning from normal combustion to heat retention 1L to lower the furnace temperature, first, the furnace temperature setting setting 10 is set to a pre-planned furnace heat retention temperature. The lower limit alarm 13 detects this heat retention temperature setting position. On the other hand, the output of the deviation calculator 12' becomes a much larger deviation immediately after the furnace temperature setting 1iii 10 is changed to the warming temperature setting 1, so this is detected by the upper limit alarm device 14. Further, through these logic operations, the switch signal of the interlock 15 which determines whether or not to set the minimum 70 and the output signals from the lower limit alarm 13 and the upper limit alarm 14 are calculated using an AND gate 16, The output of the AND gate 16 switches the switch 18 from the terminal side to the a side. As a result, the signal to the output processing 19 is switched from the preset signal from the minimum setter 20 to the signal passed through the terminal side of the switch 23. The minimum setting fiiMV1 in the minimum setting device 20 is set to the lowest setting amount that allows sustained combustion in the furnace.

Furnace temperature setting at this time [direct Sv1 furnace temperature measurement direct PV
, the temporal changes in the valve operation signal MV are shown in Figure 3(b).
This is shown below. That is, time t. When the set point is lowered to the keeping temperature, the valve operation signal MV becomes MVI at that moment.
changes slightly. If this state is left as it is, the furnace temperature d(1) constant lft and PV will start to fall, and the deviation from SV,!:PV at 8 o'clock will be the magnitude of DLI.As a result, The lower limit alarm 21 in FIG.
Minimum setting device from 0 1 Direct MVI to minimum setting device 2
The minimum setting suddenly changes from 2 to ffiMV2. In addition,
While the switch 18 is on the terminal a side, the PID calculator 17
is integrated and separated by the output of the AND gate 16, and the valve operation signal MV from the output processing section 19 is fed back immediately after reset, so the output of the PID calculator 17 is M
It is held at the same value as V2's elbow. This MV2 box shows the PID effect when the furnace temperature setting in the first shift shifts to the warm temperature and settles down in the conventional case where all of these calculation logics shown in Figure 3 (a) are not added. The final output of the converter 17 is set to 1. By doing this, the AND gate 16 is turned off at the next time t2, and the PID calculator 17 changes from the integral separation to the normal output. When shifting to PID calculation, the temperature control system is stable, so it is possible to shift to the pan press.Usually, the temperature control system is stable, so the temperature control system can be shifted to the pan press. The directivity of the deviation value) is set to be almost the same, and the LI is slightly larger, and the DH engineer sets the heat retention temperature setting [1 shift, which is 4 to 5 C higher than the direct SVI.

In this way, it is possible to smoothly shift to the PIDOX calculation at the insulating temperature without any overshoot.

The reason why the lower limit alarm 13 is provided is to enable these logic operation circuits to operate only when the temperature is set to the insulating temperature.

These logic operation circuits can be easily incorporated into DDC control using a one-loop controller or a multi-loop controller with a built-in microcomputer.

Furthermore, in a heating furnace, it is common to provide multiple temperature control devices for each furnace, but in this case, all the same logical operation circuits are installed in the total temperature control device,
It is quite possible to operate them simultaneously or sequentially.

Furthermore, when using an industrial heat treatment furnace or the like other than a heating furnace in a batch manner, it is effective to use the entire temperature control device according to the present invention.

As explained above, according to the present invention, the temperature inside the heating furnace under normal use can be lowered to the insulating temperature in a short time, and in addition, overshoot hardly occurs, and wasteful consumption of fuel can be avoided. The effect is that it can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the heating furnace temperature control device of the present invention, FIG. 2 is a block diagram showing an embodiment of the temperature controller of FIG. 1, and FIG. Trend chart when lowering the temperature setting using a conventional device, (b)
FIG. 2 is a diagram showing an example of a trend chart of matchmaking using the device according to the present invention. DESCRIPTION OF SYMBOLS 1...Heating furnace, 2...Temperature detection end, 3...Temperature converter, 4...Temperature controller, 5-Function calculator, 6...
・Fuel control valve, 7... Combustion chamber control valve, 12... Deviation calculator, 13.21... Lower limit alarm, 14... Upper limit alarm, 15... Interlock, 16. ...AND gate, 17...PID arithmetic unit, '18.23
...Switch, not shown in Figure 9'7 13 Figure

Claims (1)

[Claims] 1. Input the output of the temperature detection terminal that detects the temperature inside the heating furnace through a temperature converter, and calculate υ by the deviation from the constant number of furnace temperatures.
A temperature controller that sends out the PID-calculated output, a fuel control valve that inputs the output of the temperature controller to adjust the fuel flow rate, and inputs the output of the temperature control needle via a function calculator. Temperature control valve consisting of a combustion air control valve that adjusts the amount of combustion air
Jf: In the i & υ control device, in the temperature control #1, when the furnace temperature constant is below a predetermined lower limit ffi and the deviation from the temperature side constant is more than a predetermined standard, the temperature is adjusted. PII) The computing unit of the controller is in an integral-separation state, and outputs the operating monthly direct from the separately provided manipulated variable setting device from the temperature TF adjustment arm, while the operating monthly direct is output from the P I J ) is fed back to the calculator, and when the deviation becomes below the specified value, solve the integral separation 'fc of the I)ID calculator, and output the operating boolean direct that had been output until then from the PID calculator. A temperature control device for a heating furnace, characterized in that it is equipped with a means for switching to output.